We've recently been talking about Chancellorsville in a McClellan thread. One of the things that got me was that Hooker actually took fewer casualties percentage wise than were inflicted on Lee. If you simply look at the numbers The Army of the Potomac suffers several more thousand casualties than the Army of Northern Virginia. But if you look at the percentage of casualties to the size of the force engaged Hooker suffers 13% to 15% percent of his total force as casulaties while Lee suffers 21% to 22%. Massive defeat for hooker, but because he had the larger force (by several tens of thousand men) he takes a smaller percentage.